With growing demand for OTT and VOD content, the usage of watermarking techniques that can secure content against unauthorized usage and distribution is also on the rise. Standard watermarking techniques only help content creators identify the source of infringement, thereby creating a need for ways to recognize the specific user accounts or streaming sessions so that watermark detection can be used to identify individuals responsible for the leak and take necessary action.
This is where session-based video watermarking comes into the picture. Session-based watermarking is seen as a way to address the problem of the “analog hole” in which the availability of high-definition displays and cameras has exacerbated the unauthorized redistribution of premium content.
A sessions-based watermark can be developed by creating two versions of the same content (called A and B variants). First, the assets are segmented into chunks as done for adaptive bitrate delivery, and the playouts have a unique pattern of As and Bs. The session identifier is determined from the unique sequence of A/Bs during the reveal process. The session-based manifests are then created along with segmented lists of the various chunks and combinations, and every chunk used is either from Track A or Track B. This helps in binary representation of the content which can be used to create unique manifests for each individual session.
In this technique, only two copies of the content are created which are then cached on a CDN, which is used for DRM protected content, thereby eliminating the need for client-side third-party integrations as all the information is already present on the server-side manifests. It also eliminates the need for creating or storing as many content versions as the number of users on a content providing platform. In a well designed and executed system, session-based watermarks are difficult to tamper with or remove even if the user tries to convert the asset to analog or re-digitize, resize, recompress, or crop the asset.
Session-based watermarking is, therefore, used by studios and streaming service providers to fight against a wide range of attacks including collusion and playlist shuffling. With the advantage of server-side watermarking, it adds an additional security layer to DRM-protected content on all kinds of devices without requiring device integration.